Chondrocranium and visceral skeleton of Atelopus tricolor and Atelophryniscus chrysophorus tadpoles (Anura, Bufonidae)

2001 ◽  
Vol 22 (2) ◽  
pp. 167-177 ◽  
Author(s):  
Rafael De Sá ◽  
E.O. Lavilla

AbstractAtelopus tricolor and Atelophryniscus chrysophorus have gastromyzophorous tadpoles. Aside from specific differences, the larval chondrocrania and visceral skeletons show several shared character states, including an almost quadrangular, open chondrocranium, cornua trabeculae with expanded tips, cartilago suprarostralis as a single element, a posteriorly projected arcus subocularis quadrati, a closed muscular tunnel, and a simplified branchial basket, with only three pairs of ceratobranchiales. They are compared with diverse character states of suctorial larvae considering them as causally related to the stream life adaptations. Atelopus tricolor y Atelophryniscus chrysophorus poseen larvas gastromizóforas. Dejando de lado las diferencias específicas, los condrocráneos y esqueletos hiobranquiales larvales comparten diversos estados de carácter, incluyendo el condrocráneo cuadrangular y abierto, los cuernos trabeculares con extremos expandidos, el cartílago suprarostral como elemento único, el arco subocular proyectado hacia atrás, el túnel muscular cerrado y la cestilla branquial simplificada, con sólo tres pares de ceratobranquiales. Algunos de estos estados de carácter son comparados con aquellos de larvas suctoras considerados como causalmente relacionados a los hábitats torrentícolas, para una mejor comprensión de de la vida en ambientes de corriente rápida.

Author(s):  
Dennis Maher ◽  
David Joy ◽  
Peggy Mochel

A variety of standard specimens is needed in order to systematically investigate the instrumentation, specimen, data reduction and quantitation variables in electron energy-loss spectroscopy (EELS). Pure single element specimens (e.g. various forms of carbon) have received considerable attention to date but certain elements of interest cannot be prepared directly as thin films. Since studies of the first and second row elements in two- or multicomponent systems will be of considerable importance in microanalysis using EELS, there is a need for convenient standards containing these species. For many investigations a standard should contain the desired element, or elements, homogeneously dispersed through a suitable matrix and at an accurately known concentration. These conditions may be met by the technique of implantation.Silicon was chosen as the host lattice since its principal ionization energies, EL23 = 98 eV and Ek = 1843 eV, are well removed from the K-edges of most elements of major interest such as boron (Ek = 188 eV), carbon (Ek = 283 eV), nitrogen (Ek = 400 eV) and oxygen (Ek = 532 eV).


Author(s):  
L. T. Germinario

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.


2014 ◽  
Author(s):  
Matthew E. Harvazinski ◽  
Venkateswaran Sankaran ◽  
Douglas G. Talley
Keyword(s):  

2014 ◽  
Author(s):  
Cheng Huang ◽  
Rohan Gejji ◽  
William Anderson ◽  
Changjin Yoon ◽  
Venkateswaran Sankaran

2016 ◽  
Author(s):  
Alicia M. Cruz-Uribe ◽  
◽  
Maureen Feineman ◽  
Thomas Zack ◽  
Dorrit E. Jacob

2021 ◽  
Vol 178 ◽  
pp. 783-792
Author(s):  
Jinhyun Bae ◽  
Seokgyu Jeong ◽  
Youngbin Yoon

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